The present invention relates to a tape printing device which utilizes a tape cassette that accommodates a printable tape. In particular, the invention relates to the mechanism for cutting the tape after printing.
Known tape printing devices of the type with which the present invention is generally concerned are disclosed in EP-A-0 322 918 and EP-A-0 322 919 (Brother KK) and EP-A-0 267 890 (Varitronic). Each of these printers includes a printing device having a cassette receiving bay for receiving a cassette or tape holding case. In EP-A-0 322 918, the tape holding case houses an ink ribbon, a transparent image receiving tape and a double-sided adhesive tape which is secured at one of its adhesive coated sides to the image tape after printing and which has a backing paper peelable from its other adhesive side. In each of these devices, the image transfer medium (ink ribbon) and an image receiving tape (substrate) are in the same cassette.
A different type of tape printing apparatus is described in EP-A-0 578 372. In this printing apparatus, the substrate tape is similar to that described in EP-A-0 267 890 but is housed in its own tape holding case while the ink ribbon is similarly housed in its own tape holding case.
In all of these devices, the image receiving tape overlaps with the ink ribbon while passing to a print zone where a fixed print head and a platen, against which the print head is pressed, transfer an image from the ink ribbon to the image receiving tape. There are many ways of accomplishing this transfer, including dry lettering or dry film impression. The most usual way at present is by thermal printing, where the print head is heated and the heat causes ink from the ink ribbon to be transferred to the ink receiving tape. Alternatively, the print head may be in direct contact with a thermally sensitive image receiving tape to generate an image on the image receiving tape when the print head is heated.
When the desired image has been printed onto the image receiving tape, the user must cut off the printed portion of tape from the supply in order to use it as a label. In order to perform this cutting, there exists a variety of cutting mechanisms known in the art, including scissors (EP-A-0 267 890, EP-A-0 327 075, DE-A-4 410 931), blades acting against an anvil (EP-A-0 364 305, EP-A-0 450 779, EP-A-0 719 620), and cooperating cutting blades (EP-A-0 636 562, EP-A-0-734 818).
EP-A-0 634 275 describes a guillotine cutter which protrudes during the cutting operation into a slot of the tape cassette, while the walls of the cassette adjacent to the slot support the tape. In this arrangement, it is necessary to manufacture the cutting mechanism and the cassette within small tolerances, in order to ensure that the cutting blade travels into the cutting slot and does not contact the side walls of the slot or even the portion of the wall of the cassette which supports the tape during cutting. Small tolerances are further required to obtain a cut having an angle of exactly 90 degrees with respect to the longitudinal axis of the tape. A disadvantage of the prior art is thus the necessity to have such small tolerances, which increases productions costs.